The present invention relates in general to heated tools, and in particular to a new and useful heated tool for soldering objects to a plurality of pads which are spaced apart by a certain spacing, the heated tool including spacer bars for isolating the pads from each other. The heating tools may either be moved to the objects to be treated or connected, or mounted in a fixed position with the object to be treated or connected being brought to the heated tool.
Thermal energy is either supplied to the objects to be treated or connected, by radiant heating from heated surfaces of the tool, or by direct thermal contact between the heated tool and the object. A controlled force is usually applied against the object by the heated tool. An additional thermal conductive material may be used to increase heat flow from the heated tool to the object. Flux, for example, may be provided for increasing the transfer of heat and for reducing oxidation during the thermal process.
Such tools may supply heat either continuously or during selected time periods only. Heat may be applied during heating pulses which may be activated or controlled by various external conditions, for example, by forcing the heated tool against the object to be heated or connected.
Various sources of heat are known for heating the heated tool to a variety of selected temperatures. Hot gases and/or electric current for example may be used for heating specified heat supplying areas or surfaces of the tool.
For the present invention, it is preferable to utilize the flow of electrical current through a heated tool for heating the tool. This permits controlled pulse-heating featuring fast heating rates as well as precise temperature control at various areas of the tool.
A known generally U-shaped heated tool is disclosed in German Pat. reference No. 2,848,519. This heated tool is mounted to holders either using screws or by welding. This keeps the heat supplying areas of the tool in position and further is used to provide electrical connectors for feeding electrical heating current to the tool. Such tools can be manufactured using sheet metal designs (see German Pat. Nos. 3,144,048.7, 3,137,859.5 and 3,137,860.9 to the present inventor). These heated tools can also be machined from solid materials.
When transferring thermal energy to one or more objects using one or more heated tools, excess heat and relatively long periods of time are sometimes needed, particularly when the objects are made of materials having high thermal loads.
The use of force-controlled thermal contact for transferring thermal energy from a tool to a part must also be accurately controlled. For this reason force-controlled thermal contact has limited applications. Objects having high thermal conductivity, for example objects made of metal oxides, require different procedures. Continuous preheating for example may be necessary for such applications. A heating tool is simply set at a much higher temperature to compensate for thermal loads. This has limitation however in that excess heat may be damaging to some materials.